Symantec and McAfee had complained that without the ability to disable this software, Vista users who had purchased their products would receive duplicate and confusing security messages.

The APIs are being released via several of Microsoft's security partner programmes, including the SecureIT Alliance and the Microsoft Security Response Alliance, said Adrien Robinson, a director with Microsoft's security technology unit.

Symantec had brought this and other complaints to the European press recently and was clearly hoping to pressure the EC (European Commission) into forcing Microsoft into changes.

On Friday, Microsoft announced it would make the changes that McAfee and Symantec had been seeking. Monday's API release is the first step in this direction.

However, it appears that it may be as long as a year before Microsoft addresses a second concern, relating to a technology called PatchGuard, that Symantec and McAfee say will make their products less secure on some Windows systems.

PatchGuard is designed to prevent software from accessing the core of the Windows OS (operating system), called the kernel.

Although PatchGuard is not used by Vista in 32bit mode, it will lock many types of software, including Symantec's, out of the kernel on 64bit versions of the OS. The security vendors wanted Microsoft to give them some way to access the 64bit kernel, saying this high-level access was required in order to activate critical security features.

Most Vista users will run Vista in 32bit mode when it first ships, but the 64bit version is expected to eventually become more widely adopted because its ability to process data in larger, 64bit chunks will give it a performance edge.

Microsoft has now pledged to create new APIs for Vista that will allow vendors like Symantec to get around PatchGuard.

Those APIs will be complex, however, and it will take time for them to be developed, Robinson said. Microsoft expects to roll out this functionality in the first major SP (service pack) update to Vista. No timeline has been set for Vista SP1, but if history is a guide, it could be a year away. Microsoft rolled out SP1 for Vista's predecessor, Windows XP, nearly one year after the software's introduction.

Robinson left open the possibility that the kernel APIs could also be released ahead of Vista SP1. "If we can do something sooner, then we'd like to do that as well," she said.